1. Field of the Invention
The present invention relates to an outer retainer for a one-way clutch that is employed for an automatic transmission and the like of a vehicle.
2. Related Background Art
The automatic transmission and the like of the vehicle involves using the one-way clutch that transmits rotary force on a driving side in one direction but does not transmit the rotary force in the opposite direction.
A conventional sprag type one-way clutch is constructed of an inner race and an outer race that are concentric and make relative rotations and of a one-way clutch mechanism interposed between the inner race and the outer race. The one-way clutch mechanism is built up by a plurality of sprags defined as torque transmitting members, a spring member that biases the sprags in an engaging direction, a cylindrical inner retainer and an outer retainer which hold the sprags and restrain an excessive inclination thereof, and a pair of end bearings that ensure operations of the sprags by retaining these two retainers at a predetermined interval.
The outer retainer is constructed of two annular portions facing each other in an axial direction and a plurality of column members connecting these annular portions and provided at a predetermined interval in a peripheral direction. The outer retainer has a plurality of window portions each configured by the neighboring column members and the two annular portions at a predetermined interval in the axial direction. Further, one annular portion is formed with an outward flange directed outward in a radial direction at an end on the opposite side to the other annular portion in the axial direction, i.e., at an end of the outer retainer in the axial direction. The outward flange engages with an engagement groove formed in an inner peripheral face of the outer race, thereby positioning and supporting the outer retainer with the outer race.
The inner retainer and the outer retainer have substantially the same configuration, however, a flange of the inner retainer formed at an end in the axial direction is an inward flange directed inward in the radial direction.
In the thus-constructed one-way clutch, in the case of transmitting torque with the outer race serving as a driving race for applying rotary force to sprags, it is required to apply proper drag torque to between the outer retainer and the inner peripheral face of the outer race in order to surely transmit an operation to the sprags such as when an abrupt operation is applied to the outer race.
A known means for obtaining the drag torque is a means that forms a shaped portion called a T-bar or an i-bar in the outer retainer, gets the shaped portion deformed and thus brings the shaped portion into contact with the inner peripheral face of the outer race. The T-bar is formed by a portion of the annular portion on the side of the outward flange cut away at two portions thereof defining respectively two window portions neighboring each other and the column member between the window portions neighboring each other. In other words, this T-bar forming means configures a T-bar defined as a T-shaped portion by the column member between the neighboring window portions and the divided outward flange-sided annular portion between the two cut-away portions. A plurality of thus-formed T-bars are provided at a predetermined interval, and the column members of these T-bars are bent outward in the radial direction by a predetermined quantity. The divided and radially outward flange of the T-bar engages with an engagement groove formed in an inner peripheral face of the outer race. The flange engaging with the engagement groove serves as a mechanism for preventing a removable of the outer retainer after being assembled to the outer race.
Moreover, the i-bar defined as an i-shaped portion is formed by cutting a part of one column member, closer to the annular portion, between the neighboring window portions so as to separate the column member into two column portions. A scheme is that a plurality of the thus-configured column members are provided at a predetermined interval, one of the separated column portions of each thus-configured column member, is bent outward in the radial direction into an elastic member, the outer retainer is held on the inner peripheral face of the outer race by dint of spring action of the elastic member, and the elastic member abuts on the inner peripheral face of the outer race, thereby obtaining the drag torque.
Japanese Utility Model Laid-Open Publication No. 63-115637 discloses an outer retainer having a connected T-bar structure in which the T-bars are formed so as to be connected in the peripheral direction, and peripheral rigidity of the T-bar is thus improved.
Further, U.S. Pat. No. 5,000,303 discloses an outer retainer having a configuration that an i-bar is, as illustrated in FIG. 4, built up by providing a column member 1122 with a cut portion 1181 in an outer retainer 103, the i-bar serving as an elastic member 1161 being slid on an inner peripheral face of an outer race, and further cut-away portions 1171, 1172 are formed by cutting through annular portions 110b on the side of an outward flange 113, at portions where window portions 1151, 1154 on both sides of window portions 1152, 1153 adjacent to the elastic member are provided with the column member 1122 formed with the elastic member 1161 being centered. The portion of the annular portion 110b between the cut-away portions 1171 and 1172 get deformed to open in the peripheral direction, that is, enlarge outwardly in the radial direction. Thus, the outer retainer is deformed, whereby an outer diametrical face of the outward flange is slid on the inner peripheral face of the outer race.
As in the outer retainer illustrated in FIG. 4, however, if an interval in the peripheral direction between the cut-away portion formed in the annular portion on the outward flange side and the column member formed with the elastic member, is small, namely, if the cut-away portions are provided at the window portions existing on both the sides of the window portions adjacent to the elastic member with this elastic member being centered, the outer retainer is easy to be broken due to a stress. That is, in the case of the one-way clutch used for a starter etc, there is a sharp fluctuation in rotations as when an engine abruptly starts up, and there is the increased amplitude of the stress applied to the retainer due to centrifugal force. Consequently, if a position of the elastic member acting to support the outer retainer on the inner peripheral face of the outer race is close to a position of the cut-away portion provided at the annular portion on the side of the outward flange, a corner part (depicted by, e.g., an ellipse in FIG. 4) of the window portion is easy to be broken due to the amplitude of the stress in the annular portion on the side of the outward flange configuring the window portion formed with the cut-away portion or in the annular portion on the side having none of the outward flange. Namely, a distance from the column cut and deformed to be the elastic member to the cut away portion of the annular portion on the side of the outward flange is shorter, the amplitude of the stress is larger, and both of the corners of the window portions formed with the cut-away portion are easy to be broken.
Further, in the case of forming the cut-away portion and the elastic member simultaneously, if the interval between the cut-away portion and the elastic member is small, i.e., if the distance therebetween is short, the working apparatus itself comes to have a complicated mechanism, resulting in a rise in costs.